In this country alone, hidden insect infestation in stored agricultural commodities such as corn, wheat, rice, seeds, oats, barley, cotton, etc., costs the government and farmers millions of dollars each year. This figure is obviously larger when considered on a worldwide basis. Quick, inexpensive, and reliable tools for determining insect infestation are needed, and could prove very beneficial in: (1) determining if a stored commodity is marketable; (2) maintaining good quality of agricultural commodities, and; (3) facilitating enforcement of government food quality regulations.
Various detection methods used in the past included X-ray, chemical or visual analysis, and more recently, acoustical amplification of insect sounds as exemplified by U.S. Pat. No. 4,671,114 issued 6/9/87 to Litzkow et al. All of these methods are expensive, require elaborate testing facilities with trained personnel, and have various drawbacks. For example, X-ray inspection suffers from the drawbacks of: (1) high initial cost for equipment; (2) high cost of X-ray film and development, and; (3) examination of each of the individual grains on the X-ray film requires a great deal of labor. Acoustic detection such as that disclosed by the aforementioned U.S. Pat. No. 4,671,114 suffers from the drawbacks of: (1) requiring extensive acoustical detection elements which are not necessary for the present invention; (2) being susceptible to interference from extraneous sound thus requiring operation thereof in a sound dampened environment, in contrast to the present invention which provides similar sensitivity but surprisingly is not as susceptible to such interference.
Pitfall probe traps (some types of these are termed "Loschiavo" traps after S. R. Loschiavo who first described them in "A trap for the detection and recovery of insects in stored grain" Can. Entomol. 99:1160:1967) are commonly used in the grain industry to detect insect infestations. Insect infestation is commonly detected by burying such traps in grain, and capturing adult insects that wander into the perforated top part of the trap and fall into the reservoir located at the bottom of the trap. The trap is pulled from the grain mass by means of a rope and the number of insects captured is an indication of the level of the insect infestation in the grain. A shortcoming of this trap is that although traps can be positioned all the way to the bottom of a tall grain silo before it is filled with grain, once the trap is pulled up to check for insects, it is difficult or impossible to reinsert it in the grain to depths of more than a few feet. This invention allows the remote detection of the presence (and optionally the quantity) of insects without pulling the trap from the agricultural commodity. Thus, traps can remain in place even at considerable depths where they can continually monitor for insect infestations for an extended period of time (e.g. for a full storage season).
One embodiment described in the aforementioned parent application relates to a probe which was designed to detect insect infestations by insertion thereof in an agricultural commodity and counting the number of insect produced sounds detected by the probe. The number of insect produced sounds varies with the insect population density in the agricultural commodity and thus the population could be estimated by the number of detected sounds. There are many situations where this type of grain probe would be very useful, especially, where a quick decision was needed about whether grain was infested or not. However, the number of sounds detected by such a probe may depend both on the density of the insect infestation and on the distance between the insect and the probe. This latter parameter can make accurate estimation of the number of insects in a bin of agricultural commodity very difficult. Grain attenuates the insect produced sounds such that insects near the probe will produce many more detectable sounds than insects located farther from the probe. This attenuation can effect the estimated number of insects in the agricultural commodity by as much as 100 fold. For example, if the grain probe detected "X" number of sounds in a bin of grain, one may not know if these sounds were produced by one insect very close to the piezoelectric disc or possibly 100 insects located farther from the disc. Thus a marked improvement in insect estimation could be achieved, if this "distance" factor could be eliminated from the picture. The present invention does just that. By ensuring that all detected insects are confined in the proximity of the detection means (e.g. essentially confined on a surface of the detection means) the distance factor is removed from the infestation estimation problem.